One aspect of image processing includes human-computer interaction by detecting human forms and movements to allow interaction with images. Applications of such processing can use efficient or entertaining ways of interacting with images to define digital shapes or other data, animate objects, create expressive forms, etc.
Detecting the position and movement of a human body is referred to as “motion capture.” With motion capture techniques, mathematical descriptions of a human performer's movements are input to a computer or other processing system. Natural body movements can be used as inputs to the computer to study athletic movement, capture data for later playback or simulation, enhance analysis for medical purposes, etc.
Motion capture techniques tend to be complex. Some techniques require the human actor to wear special suits with high-visibility points at several locations. Other approaches use radio frequency or other types of emitters, multiple sensors and detectors, blue screens, extensive post processing, etc. Techniques that rely on simple visible light image capture are not accurate enough to provide well-defined and precise motion capture.
Some motion capture applications allow an actor, or user, to interact with images that are created and displayed by a computer system. For example, an actor may stand in front of a large video screen projection of several objects. The actor can move, or otherwise generate, modify, and manipulate the objects by using body movements. Different effects based on an actor's movements can be computed by the processing system and displayed on the display screen. For example, the computer system can track a path of the actor in front of the display screen and render an approximation, or artistic interpretation of the path onto the display screen. The images with which the actor interacts can be, e.g., on the floor, wall, or other surface, suspended three-dimensionally in space, displayed on one or more monitors, projection screens or other devices. Any type of display device or technology can be used to present images with which a user can control or interact.
In some applications, such as point of sale, retail advertising, promotions, arcade entertainment sites, etc., it is desirable to capture the motion of an untrained user (e.g., a person passing by) in a very unobtrusive way. Ideally, the user will not need special preparation or training and the system will not use unduly expensive equipment. Also, the method and system used to motion capture the actor should be invisible or undetectable to the user. Many real world applications must work in environments where there are complex and changing background and foreground objects, short capture intervals and other factors that can make motion capture difficult.